Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$29.27	4.250%	$30.514	$30.51	$30.50	$30.50
Purchase #2	$68.32	6.360%	$72.6652	$72.67	$72.65	$72.70
Purchase #3	$111.98	9.411%	$122.5184	$122.52	$122.50	$122.50
Purchase #4	$211.54	5.725%	$223.6507	$223.65	$223.65	$223.70
Purchase #5	$72.32	6.402%	$76.9499	$76.95	$76.95	$76.90
Purchase #6	$105.34	3.400%	$108.9216	$108.92	$108.90	$108.90
Purchase #7	$141.40	7.717%	$152.3118	$152.31	$152.30	$152.30
7 purchase totals =	$740.17		$787.5316	$787.53	$787.45	$787.50